The combination of high prices for raw materials and continually increasing labor costs has been viewed by the new-tire producing industry with great apprehension, since it is difficult to match these costs with increased production volume. Increased production costs for new tire production have increased interest within the field of tire retreading. The interest in recycling has also been a factor.
A conventional retreading plant is however expensive and has a low production capacity, i.e. the number of retreaded tires per hour.
Most conventional retreading systems work with prevulcanized treads. In all of these systems with prevulcanized treads the tire, after the old tread has been ground away, is provided with a new tread which is fixed to the carcass by means of a rubber base bonding strip, and the tire is then placed, depending on the system, in an autoclave or in a heated matrix. Heating of the autoclave or matrix is accomplished in most systems by means of steam, but electric heating is employed in some systems of both the autoclave and matrix type. The vulcanization time varies in the various systems between 1.5 and 5 hours.
According to another major system for retreading a new unvulcanized tread is used which under vulcanization is fixed to the old tire carcass.
Some of the most employed retreading systems and their most important differences are given below. The differences are mainly in the final work stages when the tread is to be fixed to the carcass.